JPH11202642A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent developer sticking to the carrying face as of a transfer belt from being transferred to a sheet unnecessarily. SOLUTION: The image forming device 10 has a photoreceptor 12, the transfer belt 36, a transfer roller 40 for transferring powder developer on the photoreceptor to the transfer belt 36, and a cleaner 22 for recovering the residual developer from the photoreceptor 12. A switching device 48 switches the transfer roller 40 back and forth between a first condition in which the developer is transferred from the photoreceptor 12 to the transfer belt 36 and a second condition in which the developer is reversely transferred from the transfer belt 36 to the photoreceptor 12. Other switching device 58 switches a recovering roller 50 back and forth between a condition in which the developer is recovered from the transfer belt 36 and a condition in which the recovered developer is released to the transfer belt 36 again. The developer released to the transfer belt 36 is reversely transferred onto the photoreceptor 12 and thereafter recovered to the cleaner 23. This prevents transfer of the unwanted developer to the sheet from the transfer belt 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a copying machine or a printer using a powder developer.

[0002]

2. Description of the Related Art As one of various image forming apparatuses conventionally proposed, a developer image formed on a photoreceptor is firstly transferred onto a rotating belt, and then the developer image is transferred to paper or the like. There is an image forming apparatus of a type that performs secondary transfer to a sheet. As another image forming apparatus, there is an image forming apparatus of a method of transferring a developer image created on a photoreceptor to a sheet held on an outer peripheral surface of a rotating belt.

[0003]

However, in the image forming apparatus using these rotating belts, there is a problem that the developer adhered to the rotating belt is transferred to a sheet and the sheet is soiled. In order to prevent this, an image forming apparatus has been proposed in which a cleaning unit is provided in the vicinity of the rotating belt to thereby remove the developer from the rotating belt. However, the cleaning unit and the accompanying device take up a large space. Therefore, there is a problem that the size of the image forming apparatus is increased.

[0004]

In order to solve such a problem, the present invention provides a rotatable endless first support surface,
A rotatable endless second supporting surface, a transfer device for transferring the powder developer carried on the first carrying surface to the second carrying surface or a sheet carried on the second carrying surface, An image forming apparatus including a first collecting device for collecting the developer from the first supporting surface, the transfer device, the developer from the first supporting surface, the second supporting surface, or the second supporting surface; A first state of transferring to a sheet carried on the
A transfer / reverse transfer switching device for switching to a second state in which the developer carried on the carrying surface is reverse-transferred to the first carrying surface, a second collecting device arranged near the second carrying surface, The second recovery device is switched between a recovery state in which the developer carried on the second support surface is recovered and a discharge state in which the developer recovered from the second support surface is again released to the second support surface. And a recovery / release switching device.

[0005]

According to this image forming apparatus, at the time of image formation, the transfer device is set to the first state by the transfer / reverse transfer switching device, and the developer on the first carrying surface is either the second carrying surface or the second carrying surface. The image is transferred to the sheet carried on the carrying surface. Also,
The second recovery device is set to the recovery state by the recovery / release switching device, and the developer carried on the second support surface is recovered by the second recovery device.

At the time of non-image formation, the second collecting device is set to the discharging state by the collecting / discharging switching device, and the developer collected by the second collecting device is discharged to the second holding surface. Further, the transfer device is set to the second state by the transfer / reverse transfer switching device, and the developer carried on the second carrying surface is reverse-transferred to the first carrying surface. The developer reversely transferred to the first support surface is collected by the first collection device.

Therefore, the developer adhered to the second support surface is not transferred to the sheet in contact with the second support surface, so that the image quality is not deteriorated and the sheet is not stained. Further, since there is no need to dispose a large cleaning unit near the second support surface as in the related art, it is possible to reduce the size of the image forming apparatus by that much, and to reduce the space around the second support surface for other purposes. Therefore, the degree of freedom in designing the image forming apparatus is increased.

In a mode in which a charging device for charging the developer carried on the second carrying surface to a predetermined polarity is provided in the vicinity of the second carrying surface, the developing device charged to a polarity opposite to the original polarity is provided. The agent is also forcibly charged to a predetermined polarity, and as a result, it is reversely transferred from the second support surface to the first support surface and collected, so that contamination of the sheet and deterioration of image quality can be further reduced.

[0009]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows main components of the image forming apparatus according to the first embodiment. This image forming apparatus 10 includes a cylindrical photoconductor 12. Photoconductor 1
Reference numeral 2 denotes a first support surface, which is an outer peripheral surface, covered with a photosensitive layer, and is rotatably supported clockwise in the drawing.
Around the photoreceptor 12, in order along the rotation direction,
The outer peripheral photosensitive layer of the photoreceptor 12 is charged with a predetermined polarity (in the present embodiment, negative polarity) and a predetermined potential by a charging roller 14, and is exposed to light corresponding to an image to be reproduced on the charged photosensitive layer to form an electrostatic charge. An exposure device 16 for forming a latent image, a developing unit 18 for visualizing an electrostatic latent image formed on the photosensitive layer with a developer,
A transfer unit 20 for transferring the developer carried on the photosensitive layer to the sheet, a first recovery device (cleaning device) 22 for recovering the developer remaining on the photosensitive layer without being transferred to the sheet, A static eliminator 24 is provided to remove the charge remaining on the photosensitive layer after the agent has been removed.

The developing unit 18 includes a support drum 26 that rotates about an axis disposed in parallel with the photoconductor 12,
The four developing devices 28Y supported by the support drum 26,
28M, 28C and 28K. These four developing units 28Y, 28M, 28C, 28K have yellow,
A developer having magenta, cyan, and black colors is stored. In the present embodiment, these developers are charged to a negative polarity. By rotating the supporting drum 26, the developing unit 18 configured as described above can rotate the developing drum 28Y, 28M, 28C or 28K.
Can be opposed to the photosensitive member 12, and the electrostatic latent image is visualized using a developer of a color stored in a developing device opposed to the photosensitive member 12.

The transfer unit 20 includes three rollers 30,
32, and an endless transfer belt 36 supported by the rollers 30, 32, and 34. The outer peripheral surface of the transfer belt 36 forms a second support surface for supporting the developer. ing. One of the three rollers 30, 32, and 34 is drivingly connected to a motor (not shown), so that the transfer belt 36 rotates counterclockwise in the drawing. Roller 30 and roller 32
Are arranged so that the belt portion supported between them can contact the outer peripheral portion of the photoconductor from the portion facing the developing unit 18 to the portion facing the cleaning device 22. A primary transfer area 38 is formed by contact between the surface and the transfer belt 36.

A transfer area 38 is provided inside the transfer belt 36.
The primary transfer roller 40 is disposed to stably contact the transfer belt portion constituting the photoreceptor 12. The primary transfer roller 40 is formed of a conductive material, and a first power supply 44 (output:
DC +500 volts) and the second power supply 46 (output: DC -1)
000 volts). The changeover switch 42 is connected to a changeover device 48. By switching the changeover switch 42 with the changeover device 48, the primary transfer roller 40 is selectively connected to the first power supply 44 or the second power supply 46. is there.

A second collection device (collection roller) 5 is provided near the outer periphery of the transfer belt portion supported by the rollers 32 and 34.
0 is provided. In the present embodiment, a brush roller having a conductive brush is used as the collection roller 50, and the tip of the brush contacts the outer peripheral surface of the transfer belt 36. In the present embodiment, the collection roller 50 moves the transfer belt 36 at a moving speed (peripheral speed) of about 1 to about 1.
It is designed to rotate clockwise at 10 times the moving speed. The collection roller 50 is connected to a first power supply 54 (output: AC -500 to -1000 volts) and a second power supply 56 (output: DC -500 volts) via a changeover switch 52. The changeover switch 52 is connected to a changeover device 58. By switching the changeover switch 52 with the changeover device 58, the collection roller 50 is selectively switched to the first device.
The power supply 54 or the second power supply 56 is connected.

A secondary transfer roller 60 is in pressure contact with the roller 34 of the three rollers that support the transfer belt 36, whereby the transfer belt 36 and the secondary transfer roller 60
The next transfer area 62 is formed on the contact surface with the second transfer area 62. Also,
The secondary transfer roller 60 is connected to a power supply 64 so that a voltage having a polarity opposite to the charging polarity of the developer can be applied to the secondary transfer roller 60.

The image forming apparatus 10 configured as above operates as follows. First, at the time of image formation, the photoconductor 12 rotates clockwise, and the outer peripheral portion of the photoconductor passing through the portion facing the charging roller 14 is charged to a predetermined polarity (negative polarity) and a predetermined potential. Light is exposed from the exposure device 16 to the charged outer periphery of the photoconductor, and an electrostatic latent image corresponding to an image to be reproduced is formed. This electrostatic latent image is visualized by the developing unit 18 as a developer image of a predetermined color.
In this embodiment, a negatively charged developer is used, and the developer adheres to a portion of the electrostatic latent image where the light has been exposed to the potential attenuation portion.

When a single-color image is formed, a developing device having a developer of a selected color faces the photoreceptor 12, and the electrostatic latent image is visualized as a developer image with the developer. When creating a multicolor image, for example, a full-color image, the exposure device 1
Exposure by 6 forms an electrostatic latent image corresponding to each color, and these electrostatic latent images are developed by a developing device having a developer of a corresponding color, and a developer image of four colors is formed on the outer peripheral surface of the photoconductor. Created sequentially.

The developer image formed on the outer peripheral surface of the photosensitive member as described above is transferred to the outer periphery of the transfer belt 36 in the transfer area 38. At this time, the switching device 48 is
Is set to the solid line position, and the primary transfer roller 40 is
4 and apply +500 volts to the primary transfer roller 40. As a result, the negatively charged developer is electrically attracted to the primary transfer roller 40 and adheres to the outer peripheral surface of the transfer belt 36. When a multicolor image is created, a plurality of developer images created on the outer peripheral surface of the photoconductor are transferred to the transfer belt 3.
6 to form a single multicolor developer image.

The developer image carried on the transfer belt 36 is
Next, in the secondary transfer area 62, the image is transferred onto a sheet 66 conveyed along a path indicated by a dashed line. Similarly, the multicolor developer image is collectively transferred to the sheet 66 in the secondary transfer area 62.

The developer carried on the photoconductor 12 is not entirely transferred to the transfer belt 36 in the primary transfer area 38, and a part of the developer remains on the photoconductor 12. Similarly, all of the developer carried on the transfer belt 36 is not transferred onto the sheet 66 in the secondary transfer area 62, and a part of the developer remains on the transfer belt 36.

The developer remaining on the photoreceptor 12 is conveyed to the opposite portion of the cleaning device 22 with the rotation of the photoreceptor 12, where it is collected by the cleaning device 22.
Next, residual charges are removed from the photoconductor 12 by the charge removing device 24.

On the other hand, the developer remaining on the transfer belt 36 is conveyed to the opposite portion of the collection roller 50 as the transfer belt 36 rotates. At this time (that is, at the time of image formation), the switching device 58 sets the switch 52 to the solid line position, and the first power supply 54 (output: AC-500 to -1000).
Is applied to the collection roller 50 (see FIG. 2). As a result, the residual developer that has reached the facing portion of the collection roller 50 is disturbed by the influence of the oscillating electric field formed by the AC output, and is scraped off by contact with the collection roller 50.

At the time of non-image formation, specifically, before or after the start of the above-described image forming operation, or when forming a plurality of images continuously, between image formation and subsequent image formation (image formation) While rotating the photoreceptor 12 and the transfer belt 36 for a predetermined period of time, the switching devices 48 and 58 respectively switch the switches 42 and 52 to the dotted line positions, and switch the transfer roller 40 and the collection roller 50 to the second power supply. 46, 5
Connect to 6.

As a result, the second power source 5
6 to -500 volts, and the transfer roller 40 is applied with -1000 volts from the second power supply 46 (FIG. 2).
reference). As a result, the negatively charged developer held by the collecting roller 50 is electrically repelled from the collecting roller 50 and discharged to the transfer belt 36. The discharged developer is conveyed to the primary transfer area 38 with the rotation of the transfer belt 36. The negatively charged developer that has reached the primary transfer area 38 is charged by a voltage −1000 applied to the transfer roller 40.
It is electrically repelled by the bolt and is reversely transferred to the photoconductor 12.
The reverse-transferred developer is conveyed to a portion facing the cleaning device 22 with the rotation of the photoconductor 12, and is collected by the cleaning device 22 here.

As described above, the developer that has unnecessarily adhered to the outer peripheral surface of the transfer belt 36 is recovered by the cleaning device 22, so that the unnecessary developer adheres to the sheet passing through the secondary transfer area 62. Never do. Therefore, a clear image free of such unnecessary developer adhesion can be obtained. In addition, since there is no need to provide a large cleaning unit around the transfer belt 36, the space around the transfer belt 36 can be used effectively.

By the way, among the developers, there are a developer which is not sufficiently charged to a predetermined polarity and a developer which is charged to the opposite polarity (poorly-charged developer). It is desirable to actively collect these poorly charged developers. For this purpose, for example, as shown in FIG. 3, a charging device (for example, a corotron-type charging device 68) is provided on the downstream side of the secondary transfer area 62 and on the upstream side of the collection roller 50 with respect to the rotation direction of the transfer belt 36. And a power supply 70 for applying a voltage (for example, -1000 volts) having the same polarity as the charging polarity of the developer to the charging device 68. The agent is charged to a predetermined polarity (negative in this embodiment) (see FIG. 4). If you do this,
Since all of the poorly charged developer is also collected by the collection device, the contamination of the sheet can be further reduced.

FIG. 5 shows a second embodiment of the present invention. In this embodiment, the image forming apparatus 100 includes the cylindrical photoconductor 1.
02, and the photoconductor 102 is supported so as to be rotatable clockwise. Around the photoreceptor 102, a charging roller 104 and an exposure device 1 are sequentially arranged in the rotation direction.
06, a developing device 108, a transfer roller 110, a cleaning device 112, and a charge removing device 114.

The image forming apparatus 100 further includes a photosensitive member 102.
To convey the sheet between the transfer roller 110 and
It has a transport belt 116. The transport belt 116 is supported by two rollers 118 and 120, and an upper belt portion extending therebetween is a photosensitive member 102 and a transfer roller 1.
10 and rotates clockwise. Further, the transfer roller 110 is
Is pressed against the photoconductor 102, so that the transfer area 12 is brought into contact with the photoconductor 102 and the conveying belt 116.
2 are formed.

The transfer roller 110 is formed of a conductive material, and is connected to the first power supply 12 via a changeover switch 124.
6 (output: DC + 500 volts) and the second power supply 128 (output: DC-1000 volts). The changeover switch 124 is connected to a changeover device 130. By switching the changeover switch 124 with the changeover device 130, a first power supply 126 is selectively provided to the transfer roller 110.
Alternatively, it is connected to the second power supply 128.

A collecting device (collecting roller) is provided near the outer peripheral surface of the lower belt portion extending between the rollers 118 and 120.
132 is provided. In the present embodiment, the collection roller 13
As 2, a brush roller having a conductive brush is used, and the tip of the brush contacts the outer peripheral surface of the transport belt 116. In the present embodiment,
The collection roller 116 is configured to rotate clockwise at a moving speed of about 1 to 10 times the moving speed (peripheral speed) of the transport belt 116. The collection roller 132 is connected to a first power supply 136 (output: AC−50) via a changeover switch 134.
0 to -1000 volts) and a second power supply 138 (output: DC -500 volts). Selector switch 13
4 is connected to a switching device 140, and this switching device 1
By switching the changeover switch 134 at 40, the collection roller 132 is selectively connected to the first power supply 136 or the second power supply 138.

A sheet feeding device 142 is disposed on the right side of the transport belt 116 in the drawing, and a sheet 144 (for example, paper) is supplied to an outer periphery of an upper belt portion of the transport belt 116. On the other hand, a fixing device 146 and a discharge tray 148 are disposed on the left side of the transport belt 116 in the drawing.

The image forming apparatus thus configured operates as follows. As in the image forming apparatus of the first embodiment, the outer peripheral surface of the photoreceptor 102 is charged to a predetermined polarity (negative polarity) and a predetermined potential by the charging device 104, and then is exposed from the exposure device 106 to An image is formed. This electrostatic latent image is visualized as a developer image of a predetermined color by the developing device 108, and is conveyed to the transfer area 122.

The sheet 144 is sent out from the sheet feeding device 142 and supplied to the upper belt portion of the transport belt 116.
With the rotation of the conveyor belt 116, the sheet is conveyed to the transfer area 122 and comes into contact with the developer image on the photoconductor 102. At this time, the switching device 130 sets the switch 124 to the solid line position, connects the transfer roller 110 to the first power source 126,
A voltage of +500 volts is applied to the transfer roller 110. As a result, the negatively charged developer is transferred to the transfer roller 1.
The sheet 144 is electrically sucked and adheres to the surface of the sheet 144 facing the photoconductor. Next, the sheet 144 is conveyed to the fixing device 146, where the developer image is fixed,
It is discharged to 48.

The developer remaining on the photoreceptor 102 is
The photoconductor 102 is conveyed to the opposite portion of the cleaning device 112 with the rotation of the photoconductor 102, and is collected by the cleaning device 112. Next, the residual charge of the photoconductor 102 is removed by the charge removing device 114.

On the other hand, the developer remaining on the transfer belt 116 is collected by the collection roller 1 as the transfer belt 116 rotates.
32. At this time (that is, at the time of image formation), the switching device 140 sets the changeover switch 134 to the solid line position, and the first power supply 136 (output: AC-500 to-
1000 volts) is applied to the collection roller 132. As a result, the residual developer that has reached the opposing portion of the collection roller 132 is disturbed by the influence of the oscillating electric field formed by the AC output, and is scraped off by the contact of the collection roller 132 with the brush.

At the time of non-image formation, specifically, before or after the start of the above-described image forming operation, or when forming a plurality of images continuously, between image formation and subsequent image formation (image formation) The photoreceptor 102 and the transfer belt 11
While rotating 6, the switching devices 130 and 140 respectively switch the changeover switches 124 and 134 to the dotted line positions, and connect the transfer roller 110 and the collection roller 132 to the second power supplies 128 and 138, respectively.

As a result, −500 volts is applied to the collection roller 132 from the second power supply 138 and the transfer roller 11
0 is supplied with −1000 volts from the second power supply 128. Thus, the negatively charged developer held by the collection roller 132 is repelled by the collection roller 132 and discharged to the transport belt 116. The discharged developer is transported to the transfer area 122 with the rotation of the transport belt 116. The negatively charged developer that has reached the transfer area 122 is charged by a voltage −100 applied to the transfer roller 110.
It is electrically repelled to 0 volts and reversely transferred to the photoconductor 102. The reversely transferred developer is conveyed to a portion facing the cleaning device 112 with the rotation of the photoconductor 102, and is collected by the cleaning device 112.

As described above, since the developer that has unnecessarily adhered to the outer peripheral surface of the transport belt 116 is recovered by the cleaning device 112, the unnecessary developer may adhere to the sheet passing through the transfer area 122 after that. There is no. for that reason,
It is possible to obtain a beautiful image free of such unnecessary developer adhesion. Further, since there is no need to provide a large cleaning unit around the transport belt 116, the space around the transport belt 116 can be used effectively.

FIG. 6 shows an image forming apparatus 20 according to the third embodiment.
0, this image forming apparatus is similar to the image forming apparatus of the first embodiment except for the following points, and similar parts are denoted by the same reference numbers plus 200. . The first difference from the first embodiment is that, in the first embodiment, four developing units are supported by one supporting drum, whereas in the image forming apparatus of the present embodiment, four developing units are supported. Of the developing units 228Y, 228M, 228C, and 228K are disposed so as to face the photoconductor 212, respectively.
The second difference is that a transfer drum 236 is used instead of the transfer belt.
And a sheet 26 held on the outer peripheral surface thereof.
6 is such that the developer is transferred from the photoconductor 212.

The image forming apparatus 200 also has the same structure as the image forming apparatus 10 of the first embodiment.
And the transfer drum 236 while rotating the transfer drum 236
The developer adhered to is temporarily collected by the collection roller 250, is reversely transferred from the transfer drum 236 to the photosensitive member 212 during non-image formation, and is collected by the cleaning device 222. Therefore, unnecessary images are not adhered to the sheet that comes into contact with the transfer drum 236, and a clear image is obtained.

In the present embodiment, similarly to the modification of the first embodiment (see FIG. 3), a charging device is provided near the transfer drum 236, and the poorly charged developer or the opposite polarity charged developer is supplied with a predetermined polarity and By charging to a predetermined potential, the collection efficiency can be increased.

FIG. 7 shows a fourth embodiment of the present invention. In the copying machine 300, a transport belt 306 is rotatably supported by a pair of rollers 302 and 304 arranged in parallel with the same horizontal plane. Four photosensitive members 308 are arranged at equal intervals near the outer periphery of the transfer belt portion (upper transfer belt portion) extending between the rollers 302 and 304. Around each photoconductor 308, a charging device 310, an exposure device 31
2, a developing device 314, a cleaning device 316, and a charge removing device 318 are arranged. In each of the developing devices 314, a developer of a different color is stored. In the present embodiment, a black developer is stored in a developing device arranged at the most upstream side with respect to the rotation direction of the transport belt 306. Yellow, magenta, and cyan developers are accommodated in developing devices arranged on the downstream side, respectively.

Inside the transport belt 306, transfer rollers 320 are disposed so as to face the respective photoconductors 308. Of these transfer rollers 320, the transport belt 30
Photoreceptor 3 disposed at the most upstream side in the rotation direction
The transfer roller 320 facing the transfer switch 10
2 via a first power supply 324 (output: +500 volts)
And a second power supply 326 (output: -1000 volts). The changeover switch 322 is connected to a changeover device 328. Based on a signal from the changeover device 328, the transfer roller 320 applies a direct current of +500 volts or -1.
One of 000 volts can be selectively applied. The other transfer rollers except for the transfer roller 320 at the most upstream are connected only to the power source 324 (output +500 volts).

A collection device (collection roller) is provided near the outer peripheral surface of the lower belt portion extending between the rollers 302 and 304.
330 is provided. In the present embodiment, the collection roller 33
As 0, a brush roller having a conductive brush is used, and the tip of the brush contacts the outer peripheral surface of the transport belt 306. In the present embodiment,
The collection roller 330 is configured to rotate clockwise at a moving speed that is approximately 1 to 10 times the moving speed (peripheral speed) of the transport belt 306. The collection roller 330 is connected to a first power supply 334 (output: AC-50) through a changeover switch 332.
0 to -1000 volts) and a second power supply 336 (output: DC -500 volts). Switch 33
2 is connected to a switching device 338,
By switching the changeover switch 332 at 38, the collection roller 330 is selectively connected to the first power supply 334 or the second power supply 336.

A sheet feeding device 340 is provided on the right side of the transport belt 306 in the figure, and a sheet 342 is stored therein. On the other hand, a fixing device 344 and a paper discharge tray 346 are disposed on the left side of the transport belt 306 in the drawing.

According to the copying machine 300 configured as described above, developer images of different colors are formed on the outer peripheral surface of each photoconductor 308 according to the above-described developer image forming process. On the other hand, the paper 342 sent out from the paper supply unit 330 is held by the transport belt 306, and the respective developers are transferred to the opposing portions of the respective photoconductors 308 as the transport belt 306 rotates. The paper 342 to which the four color developers have been transferred is then conveyed to a fixing device 344, where the developer image is fixed, and then discharged to a paper discharge tray 346. On the other hand, the developer remaining on each photoconductor 310 without being transferred to the paper 342 is collected by each cleaning device 316. Further, the charge remaining on each photoconductor 308 after the transfer is removed by the corresponding static eliminator 318 to prepare for the subsequent charging.

At the time of image formation, +0.5 kV is applied to each transfer roller 320, whereby each negative polarity developer held on the photosensitive member 308 is electrically attracted to the transfer roller 320, respectively. The image is transferred to the sheet 342. On the other hand, the developer remaining on the transport belt 306 is transported to the opposite portion of the collection roller 330 as the transport belt 306 rotates. At this time (i.e., at the time of image formation), the switching device 338 sets the switch 332 to the solid line position, and the first power supply 334 (output: AC-500 to -1).
000 volts) is applied to the collection roller 330. As a result, the residual developer that has reached the opposing portion of the collection roller 330 is disturbed under the influence of the oscillating electric field formed by the AC output, and is scraped off by contact with the collection roller 330.

At the time of non-image formation, specifically, before or after the start of the above-described image forming operation, or when forming a plurality of images continuously, between the image formation and the subsequent image formation (image formation) The photoconductor 308 and the conveyor belt 30
While rotating 6, the switching devices 328 and 338 respectively switch the changeover switches 322 and 332 to the dotted line positions, and connect the transfer roller 320 and the collection roller 330 to the second power supplies 326 and 336, respectively.

As a result, −500 volts is applied to the collection roller 330 from the second power supply 336 and the transfer roller 32
0 is supplied with -1000 volts from the second power supply 326. As a result, the negatively charged developer held by the collecting roller 330 is repelled by the collecting roller 330 and discharged to the transport belt 306. The discharged developer is transported to the transfer area 322 with the rotation of the transport belt 306. The negatively charged developer that has reached the transfer area 322 is charged by a voltage −100 applied to the transfer roller 320.
It is electrically repelled to 0 volts and reversely transferred to the photoconductor 308. The reverse-transferred developer is conveyed to a portion facing the cleaning device 316 with the rotation of the photoconductor 308, and is collected by the cleaning device 316.

In the image forming apparatus of the present embodiment, the photosensitive member 3 on the most upstream side for collecting the developer on the conveyor belt 306 is used.
It is preferable that the capacity of the cleaning device 316 provided for the cleaning device 08 be larger than the capacity of the cleaning device provided for the other photosensitive members.

Further, the developer on the conveyor belt 306 is collected in the cleaning device 316 provided corresponding to the photosensitive member 308 arranged on the most upstream side in the rotation direction of the conveyor belt 306. Photoconductor 308
Are connected to the first and second DC power supplies via a changeover switch, and the cleaning devices 316 provided for the respective photoconductors 308 are connected.
Alternatively, the developer may be collected from the transport belt 306.

In this case, each of the cleaning devices 316 is provided with a detector for detecting whether or not the amount of the collected developer reaches a predetermined amount. The developer is collected, and when the amount of the collected developer in the cleaning device 316 on the most upstream side is equal to or more than a predetermined amount, the amount of the developer becomes 2 in the belt rotation direction.
It is preferable that the developer on the transport belt 306 is collected by the cleaning device 316 attached to the second photosensitive member 308, and thereafter, similarly moved to the downstream cleaning device.

In the above embodiment, the residual developer on the photosensitive member and the transfer belt is collected in the cleaning device.
As proposed in recent years, in the case of a cleanerless image forming apparatus that collects the residual developer in the developing device or the developing device, the residual developer may be collected in the developing device or the developing device.

In the above embodiment, the transfer roller is used as the transfer device. However, other types of transfer devices (for example, corotron and scorotron) can be used.

Further, in the above embodiment, the brush roller is used as a device for collecting the developer from around the belt or the drum, but a cylindrical roller may be used.

Furthermore, in the above-described embodiment, a developer that is charged to a negative polarity is used as the developer, but the charged polarity of the developer is not limited to this. Further, the polarity of the voltage applied to the transfer device and the recovery device may be changed according to the charging polarity of the developer.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a main part of an image forming apparatus according to a first embodiment of the invention.

FIG. 2 is a timing chart illustrating the operation of the image forming apparatus according to the first embodiment.

FIG. 3 is a schematic sectional view illustrating a main part of an image forming apparatus according to a second embodiment of the invention.

FIG. 4 is a timing chart illustrating the operation of the image forming apparatus according to the second embodiment.

FIG. 5 is a schematic sectional view illustrating a main part of an image forming apparatus according to a third embodiment of the invention.

FIG. 6 is a schematic sectional view illustrating a main part of an image forming apparatus according to a fourth embodiment of the invention.

FIG. 7 is a schematic sectional view illustrating a main part of an image forming apparatus according to a fifth embodiment of the invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus, 12 ... Photoconductor, 22 ... Cleaning device, 40 ... Transfer roller, 48 ... Switching device, 50 ... Collection roller, 58 ... Switching device.

Claims (2)

[Claims] 1. A rotatable endless first support surface, a rotatable endless second support surface, and a powder developer supported on the first support surface, wherein the powder developer is supported on the second support surface or the second support surface. (2) a transfer device for transferring to a sheet carried on the carrying surface;
An image forming apparatus comprising: a first recovery device that recovers a developer from a support surface; wherein the transfer device is configured to support the developer from the first support surface on the second support surface or the second support surface. A transfer / reverse transfer switching device for switching between a first state in which the developer is transferred to a sheet that is being transferred and a second state in which the developer carried on the second carrying surface is reversely transferred to the first carrying surface; A second recovery device disposed near the support surface, a recovery state in which the second recovery device recovers the developer carried on the second support surface, and a developer recovered from the second support surface And a recovery / release switching device for switching to a release state in which is released to the second support surface again. 2. The image forming apparatus according to claim 1, further comprising a charging device that charges the developer carried on the second carrying surface to a predetermined polarity.